In the traditional forming of implantable medical electrical leads, one or more wires are wound on a mandrel so as to form a coil. The wires are wrapped with enough tension to cause the wires to exceed their yield point and thus to hold a coiled shape. The pitch of a coil may range from close wound, that approaching the wire diameter or the sum of the wire diameters, for multi-wire coils, to space wound, that exceeding the wire diameter or sum of the wire diameters. The coil may be one of several conductors included in an implantable lead body and the coil may be formed from multiple insulated wires as a multi-conductor coil. The lead body is usually constructed having an outer polymeric sheath encasing the conductors, which may be arranged coaxially or co-linearly and are insulated from one another. A distal end of each conductor is coupled to one or more electrodes while a proximal end of each conductor is coupled to a contact of a connector that is in turn coupled to an implantable pulse generator (IPG) or an implantable cardioverter defibrillator (ICD). The distal end of the lead is implanted to be positioned within the heart so that the electrodes may deliver pacing and or defibrillation therapy by both sensing electrical activity of the heart muscle and stimulating the heart muscle.
Each conductor is typically coupled to a corresponding electrode, which has been formed as a separate component, such as a ring electrode, a coil electrode or a tip electrode. In designing and constructing joints between the conductors and the electrodes care must be taken to form reliable mechanical and electrical coupling; it is also desirable that the joints do not increase the profile of the lead body. Eliminating as many joints as is practical in the construction of a lead may improve the reliability of the lead and increase the ease of manufacturing.